Detection of Water Leakage in Underground Tunnels Using Corrected Intensity Data and 3D Point Cloud of Terrestrial Laser Scanning

Detection of water leakage is one of the most important regular tasks for underground tunnel inspection. In this paper, a new method is proposed for the water leakage detection in underground tunnels by using the corrected intensity data and 3-D point cloud of a terrestrial laser scanning (TLS) sensor. In the proposed method, the distance effect on the TLS intensity is first corrected based on a piecewise linear interpolation by using a reference target. Then, the distance-corrected intensity data are used to determine the surface roughness parameter that is specially considered to correct the incident angle effect. After corrections of distance and incident angle effects, the corrected intensity data are used to detect the water leakage regions in the underground tunnel. Finally, the appendages on the tunnel wall are removed by using the 3-D point cloud data to eliminate their influence on water leakage detection. To validate the feasibility of the proposed method, a case study in an underground tunnel in Beijing, China, was conducted by using a TLS sensor. Experimental results have demonstrated that the water leakage regions in the underground tunnel can be well extracted by using the corrected intensity data and 3-D point cloud, especially when the surface roughness is considered.